While working as a cashier for a New York City bar in the early 1950s, Howard Prince is surprised by a visit from his school friend Alfred Miller, now a successful television writer. Alfred confides that television networks will no longer buy his scripts because he has been placed on an unofficial “blacklist” due to his Communist sympathies. When Alfred says his only hope is to have another person act as a “front” for his work, Howard agrees to put his name on Alfred’s scripts free of charge, but Alfred insists on paying ten percent of each script sale. Howard, who is perpetually in debt from his work on the side as a bookmaker, is thrilled by the arrangement. When Howard borrows money from his brother, a furrier named Myer Prince, to pay off bets placed by local merchants, including fruit seller Danny LaGattuta, he insists that he is on the verge of a lucrative career. Back at his ramshackle apartment, Howard receives his first phone call from one of Alfred’s clients. Pretending to be the writer of Alfred’s script, Howard goes to the television studio where a half-hour dramatic program called Grand Central is in production. There, he meets producer Phil Sussman and script editor Florence Barrett, who is enamored by what she believes to be Howard’s writing. The show’s star and narrator, Hecky Brown, joins Phil and Florence in praise of the script and Howard is tasked with rewrites. Sometime later, Francis X. Hennessey, an investigator at the Freedom of Information Service bureau, receives a phone call from television network executive Tom Hampton, who requests an investigation to clear Howard of any past Communist affiliations. As Hecky Brown waits in Hennessey’s office, the investigator promises Hampton that he will report back on his interview with the actor. Hecky claims he is disinterested in politics but he confesses to marching in a May Day parade and subscribing to the Daily Worker to impress a love interest. Unmoved, Hennessey suggests that Hecky can save his career by writing a letter to “repent sincerely” and name Communist affiliates. Sometime later, Howard’s fronted episode airs on live television to great acclaim. Basking in his newfound success, Howard takes Florence to lunch at a fancy restaurant. Although she is romantically involved with a stockbroker, she is attracted to Howard’s flair for writing and agrees to another date, provoking Howard to stock up on classic American novels at a used bookstore. Still pressured to make good on his bookmaking debts, Howard visits Alfred and offers to front for additional blacklisted writers. Despite Alfred’s accusation that Howard is exploiting writers for financial gain, he introduces Howard to Herbert “Herb” Delaney and William Phelps. At a local diner, the men strategize about how to protect Howard from income tax scrutiny, but Howard tells them not to worry and later settles his debts in cash. Meanwhile, television executive Hampton learns from Hennessey that Howard has no ties to the Communist Party. While producer Phil Sussman is relieved because Howard is his only remaining writer on Grand Central, Hampton announces that Hecky’s letter was deemed unsatisfactory; Phil is ordered to fire his star performer. Over time, Howard continues to submit scripts on behalf of his friends. He buys tailored suits and moves into a high-end apartment. One day, as he delivers the script for a new episode to the television studio, Howard is ordered by Phil and Florence to rewrite a previous script on the spot, but he discreetly retrieves the edits from Alfred. That evening, Phil joins Florence in Hecky’s dressing room to report that his character must be eliminated from Grand Central. Despite Phil’s insistence to the contrary, Hecky assumes the dismissal is a result of his failed letter to Hennessey and Florence runs from the room in dismay. Sometime later, Hecky returns to Hennessey’s Freedom of Information Service office to beg for lenience, claiming he can no longer find work to support his family. Although Hennessey is indifferent, he suggests that Hecky will find more employers if he offers his services as a spy and reports on Howard’s associates. That evening, Florence arrives at Howard’s apartment, declaring that she left Grand Central in protest of Hecky’s dismissal. She intends to publish a pamphlet that exposes the injustice of the blacklist and enlists Howard as its writer, but he fears losing his celebrity and urges her to keep quiet. Florence accuses Howard of prioritizing success over human rights and leaves. Howard is eager to get out of town after the fight with Florence and agrees to drive Hecky to his latest job -- a club performance at a Catskill Mountain resort. On the way, Hecky reports that he once earned $3,000 a night, but the upcoming show will only gross $500 because of his recent blacklisting. When they arrive, the club owner professes he can pay just $300. Despite the slight, Hecky performs to a standing ovation. Afterwards, as Hecky becomes intoxicated at the bar, the club owner gives him $250 and Hecky lunges into an attack. Howard escorts Hecky back to his New York City apartment and invites the performer to stay the night. As Howard stirs in his bedroom, Hecky secretly lifts his host’s address book to make good on his deal with Hennessey. Sometime later, an FBI agent trails Howard from his bank to a meeting with Alfred, Herb and William at a nearby dinner. The agent then follows Howard as he visits Florence at her new bookstore job. He listens as Howard denounces the blacklist to get back into Florence’s good graces. The next day, Howard receives a subpoena to appear before the House Un-American Activities Committee to testify about his presumed Communist affiliates, including Florence. At a meeting with the television network lawyer, Howard agrees to recite a prewritten, anti-Communist testimony and act as a ‘”friendly witness.” However, when Hecky commits suicide and Howard observes the FBI agent taking photographs of funeral attendees, he grows increasingly aware of the injustice. Howard visits Florence and confesses that he is a front. Acknowledging the betrayal, he vows that Florence will know who he really is after his testimony. At the House Un-American Activities Committee hearing, Howard surprises his lawyer and the committee members by refusing to cooperate. Howard is threatened with imprisonment for bookmaking and for contempt of Congress, but his lawyer negotiates a deal: Howard can return to work if he identifies Hecky Brown as a Communist. Howard disparages the committee and walks out. Later, a handcuffed Howard kisses Florence in front of the train that will take him to prison. Alfred, William and Herb bid their friend farewell as a crowd of supporters wave placards that declare Howard a hero.